Near Field Imaging is used to monitor, for example, human movement in room facilities. Near Field Imaging systems are used in floor mounted planar sensors, whereby information is retrieved about the persons' location and condition by measuring the change in impedance caused by a conductive object, e.g. a human. Such arrangement can be applied in many applications, for instance senior homes etc. to observe senior citizens, or airports for monitoring movement of the passengers.
One such Near Field Imaging related planar sensoring system which is specifically suitable for senior citizens home monitoring is presented in WO2005020171. Such a system can be used to monitor vital signs of, among other things, a nursing home resident that has fallen. The floor sensor transmits the position, respiratory rate and pulse of the resident to a nurse room monitor. The most central component of the system is a sensor covering the entire apartment floor. The sensor is installed under the floor covering. The sensor has a printed pattern which is made of metal or graphite dye. This kind of sensor can be installed under conventional floor coating structures like parquet or plastic mat.
Further, WO2006003245 and WO2008068387 disclose sensor structures where the sensors are web-like and consist of several sequential electrically conducting areas in the same plane. Tracking of the object on the sensor, like a human, is based on the capacitance change between adjacent electrically conducting areas in the same plane.
Electrically conducting areas are typically metal, and they can be formed on a flexible circuit board acting as a substrate, for example, as printed layers, laminate layers, etched layers, or as foils. The metal is typically aluminium or copper and the conducting areas are connected to the system controlling electronic control unit next to the sensor by each with their own connecting wire, as is presented in WO2008068387A1.
A problem with the prior art floor sensor systems is that the sensor is installed separately from the flooring, ie. first the sensor is installed on the floor and after that the flooring is installed on the sensor. The separate installation of the sensor and the flooring is time consuming and complex. A further problem with the prior art sensor systems is the complex contact arrangement between the sensor conductors and the connection cable.